1. Field of the Invention
The present invention generally relates to a method for solidifying and sealing in a toxic substance by using sulfur.
The present invention relates to a method for solidifying and sealing (blocking) in a toxic substance with sulfur, to detoxify that toxic substance. More specifically, the present invention relates to a method of solidifying and sealing in a toxic substance including, but not limited to, organochlorine compounds, such as PCBs, and heavy metals, with sulfur, to detoxify that toxic substance, additionally to obtain therefrom a molded product that may be reusable.
Further, the present invention relates to a method of manufacturing materials made of raw materials particularly waste materials such as slag and/or dust resulting particularly from metal processing such as steel-making, and solidified with sulfur. More particularly, the present invention relates to a method of manufacturing molded materials made of raw materials particularly waste materials such as slag and/or dust resulting particularly from metal processing such as steel-making, and solidified by sulfur.
The term "molded materials" used herein refers collectively to materials molded into various shapes, as well as materials cooled with water or some other method into a granular form, which can be used as is, or later melted and molded into various shapes, for various purposes.
2. Background of the Art
Conventionally, slag and/or dust resulting particularly from metal processing such as steel-making, as well as other waste materials, etc., are directly discarded in a site for waste materials disposal because a suitable treatment method has not been found. However, recently, with a view to reducing and/or detoxifying waste materials and, additionally, effectively utilizing resources, reduction and/or detoxification of waste materials and, additionally, utilization of reclaimed resources, that is, recycling of resources, is noted and studied. The need for establishing a concrete and practical technique for reducing or detoxifying waste materials and, additionally, recycling of resources has been pointed out.
Given the above background, reclaiming and utilizing or solidifying and sealing waste materials, such as fly ash and slag resulting particularly from metal processing such as steel-making, has been studied in various ways. However, a satisfactory method has not yet been developed.
The present inventors, having keenly studied in various ways the method and apparatus, found that it was not always practically easy to obtain materials solidified with sulfur and, if necessary, molded, by melting sulfur at high temperature and mixing it with waste materials under high temperature. The present inventors also found that there were some problems in the conventional method regarding the quality of molded materials solidified with sulfur and operations to make the molded materials.
In particular, products that resulted from solidifying fly ash with sulfur were low in physical strength and sometimes caused cracks. Further, when slag and/or dust resulting particularly from metal processing such as steel-making were mixed with melted sulfur under high temperature for producing molded materials, in the presence of iron in the slag and/or dust, irritating sulfurous acid gas was often generated. This adversely affected the molding operation environment, making a deodorizing apparatus indispensable to prevent secondary pollution by the molding operation. In addition to the above, only molded materials that were unsatisfactory in physical strength were obtained, and sometimes the molded materials were cracked.
The following fourteen (14) patents were uncovered in the pertinent field of the present invention:
1. U.S. Pat. No. 3,720,609 issued to Smith et al. on Mar. 13, 1973 for "Process For Treating Aqueous Chemical Waste materials Sludges And Composition Produced Thereby" (hereafter "the '609 Smith Patent"); PA1 2. U.S. Pat. No. 3,962,080 issued to Dulin et al. on Jun. 8, 1976 for "Sodium Sulfur Oxides Waste Materials Disposal Process" (hereafter "the Dulin Patent"); PA1 3. U.S. Pat. No. 4,108,677 issued to Valiga on Aug. 22, 1978 for "Process For Treating Waste materials Sludge From Combustion Plant Desulfurization Units And Comentitious Product of The Process" (hereafter "the Valiga Patent"); PA1 4. U.S. Pat. No. 4,342,732 issued to Smith on Aug. 3, 1982 for "Sludge Fixation And Stabilization" (hereafter "the '732 Smith Patent"); PA1 5. U.S. Pat. No. 4,354,876 issued to Webster on Oct. 19, 1982 for "Utilization of Dry Scrubber Waste Materials" (hereafter "the Webster Patent"); PA1 6. U.S. Pat. No. 4,354,942 issued to Kaczur et al. on Oct. 19, 1982 for "Stabilization Of Mercury In Mercury-Containing Materials" (hereafter "the Kaczur Patent"); PA1 7. U.S. Pat. No. 4,844,815 issued to Ader et al. on Jul. 4, 1989 for "Stabilization Of Mercury-Containing Waste materials" (hereafter "the Ader Patent"); PA1 8. U.S. Pat. No. 5,304,706 issued to Hooykaas on Apr. 19, 1994 for "Fixing Agent For Fixing Organic And Inorganic Impurities Containing Material, Method For Fixing Such Material And A Synthetic Clay Material" (hereafter "the Hooykaas Patent"); PA1 9. U.S. Pat. No. 5,362,319 issued to Johnson on Nov. 8, 1994 for "Process For Treating Fly Ash And Bottom Ash And The Resulting Product" (hereafter "the Johnson Patent"); PA1 10. Soviet Patent No. 761,437 (hereafter "the Soviet Patent"); PA1 11. JP-B-2-30751 ("JP-B" means examined Japanese patent publication); PA1 12. East German Patent No. 288,099 (hereafter "the East German Patent"); PA1 13. JP-A-9-194737 ("JP-A" means unexamined published Japanese patent application); and PA1 14. DE 37 07 257 A1.
The '609 Smith Patent discloses a process for treating aqueous chemical waste materials sludge and compositions produced thereby.
The Dulin Patent discloses a sodium sulfur oxide waste material disposal process.
The Valiga Patent discloses a process for treating waste materials sludge from combustion plant desulfurization units and cementitious product of the process.
The '732 Smith Patent discloses sludge fixation and stabilization.
The Webster Patent discloses the utilization of dry scrubber waste materials.
The Kaczur Patent discloses a stabilization of mercury in mercury-containing materials.
The Ader Patent discloses a stabilization of mercury-containing waste materials. It is a method which involves a chemical reaction in which sulfur is reacted with a base to form a sulfide which is then reacted with the mercury to form a new compound, insoluble mercury sulfide, which is then encapsulated (at a macro level) with cement created from cement dust and water.
The Hooykaas Patent discloses a fixing agent for fixing organic and inorganic impurity containing material, method for fixing such material and a synthetic clay material.
The Johnson Patent discloses a process for treating fly ash and bottom ash and the resulting product.
The Soviet Patent discloses a complex concrete mix modifier composition containing acid vat residue of raw benzene fractionation, sodium carbonate and sulphite waste materials liquor to improve plasticity.
JP-B-2-30751 discloses a process for solidifying industrial waste material, which comprises coating industrial waste materials containing sulphates with synthetic or natural resins, and then solidifying the resultant coated matter by cement.
The East German Patent discloses a process and arrangement for conversion of sulphur waste materials into disposable products. It extracts sulphur from combustion gases into a scraper belt trough and mixes with rust ash.
JP-A-9-194737 discloses a sulfur-asphalt composition being low in ignitability, high in compression strength, resistant to granulation, and stable in solid state.
DE 37 07 257 A1 discloses a method for direct embedding of solidified, especially toxic and/or radioactive materials, especially waste, existing in a loose state, in a storage container. In DE 37 07 257 A1, sulfur is used in specific conditions, that is, in the presence of NaCl, KCl in high amounts, e.g. 40 to 50 wt %.
In the above patents, there are no disclosure or teaching of the solidification and sealing of a toxic substance in a high concentration.
It is highly desirable to provide an efficient process which utilizes elemental sulfur, sulfur-based materials, sulfur-based compounds or sulfur-based substances for the safe disposal of matter, including but not limited to, all toxic substances and other hazardous substances (solids and liquids) into a form that renders the matter non-toxic and additionally reusable.
On the other hand, among toxic substances, although PCBs (polychlorinated biphenyls) were used as a heating medium, an oil for transformers, etc., their use is now prohibited, except in some fields, since they remain in the environment for a long time and are highly toxic to the human body. Environmental pollution from the outflow of PCBs or the like from waste PCBs that have been used and stored, remains, however, a serious social problem.
To detoxify PCBS, the complete combustion method, the hydrothermal decomposition method (supercritical method); the dechlorination method, wherein light or radiation is used, and the like can be mentioned, and the final disposal place for waste PCBs, their incineration ash, etc., is required to be provided with a water barrier structure or the like. Other toxic substances besides PCBs, such as organochlorine compounds other than PCBs, are also required to be detoxified in the similar manner or processed in a final disposal place. However, since all of these means requires high-cost facilities, it is pointed out that a technique of detoxifying these toxic substances readily at a low cost needs to be established.
Under these circumstances, various investigations have been made to solidify and seal toxic substances, including organochlorine compounds, such as PCBs. However, a method has not yet been developed that is satisfactory in that toxic compounds can be prevented from leaching out, and, in addition, in that the reclaimed product can be utilized effectively, for example, a method has not yet been developed where the reclaimed product attains physical properties that allow it to be used, for example, as a building or construction material.